little or no
light is thrown on that much-contested point--the true nature of the
ovule of Gymnosperms.

=Relative position of organs.=--When organs are considered, not
separately, but in their relations to each other, the appearances
presented are referable to similar causes. Thus, the separation of parts
usually united has been shown to depend on an excess of development,
the persistent union of parts, usually separate in the adult state, has
been traced to an arrest of the process of development, by no means
necessarily coexistent with diminished growth. The diminished or
increased number of parts is, in like manner, attributable to analogous
causes, as also are the variations in arrangement and form, spoken of
under the heads of Displacement, Peloria, Substitution, &c.

In the instance of displacements, it has been shown how slight a change
is required to transform the so-called inferior ovary into a superior
one. A defective development of the top of the flower-stalk in some
cases, in others a lack of union between the tube of the receptacle or
of the calyx (comprising in those terms not only the apex of the
receptacle, but the base of the sepals) and the carpels, suffice to
bring about this change in a character which for systematic purposes is
of great value.

=Law of alternation.=--The circumstances that interfere with the law of
alternation may be briefly alluded to. The deviations from the customary
arrangement have been very generally attributed to suppression, or to
chorisis. It is unquestionable that either of these affords an efficient
explanation of the arrangement in question, as also does that
modification of chorisis, as it may be considered, which has been
treated of under the head of Enation. Spiral torsion of the axis would
likewise bring about analogous results. Still, it is quite conceivable
that opposition or superposition of organs may occur without the
intervention of any such operations. This will be the more readily
conceded when it is remembered that the phyllotaxis of leaves not
unfrequently varies on different branches of the same individual tree,
and that a similar variation in the flower would at once disturb the
customary alternate arrangement. Coalescence of the vascular bundles in
an unusual manner, and an irregular disposition of these cords have
also been considered to bring about deviations from the rule of
alternation, but in general the formation of the cords is subsequent to